Abstract: Systems and methods for fabricating bodies (e.g., porous bodies) are described. Various aspects provide for reactors and the fabrication of reactors. Some reactors include surfaces that provide for heterogeneous reactions involving a fluid (and/or components thereof). A fluid may be a gas and/or a liquid. A contaminant in the fluid (e.g., a dissolved or suspended substance) may react in a reaction. A contaminant may be filtered from a fluid. Some reactors provide for independent control of heat transfer (between the fluid, the reactor, and the environment) with respect to mass transfer (e.g., fluid flow through the reactor).